Notes of the GvSIG 2.0 workshop

This are the notes that I took over gvSIG 2.0 on the latests Jornadas GvSIG.

Pre-requisites:

  • Java
  • Eclipse
  • Ant (should)
  • Maven (should)
  • gvSIG (this is recursive :))

The main advantage of gvSIG 2.0 is that you can create a new plugin without knowing how does gvSIG work or having to compile it. We already have a gvSIG installation that deploys the binaries to the workspace. But we don’t have to change the source code of gvSIG, unless something doesn’t work (bugs) or we have to add some new functionality to the core. Better if you don’t touch it,ask the gvSIG developers and they will take care

With the binary, there is a wizard which creates an Eclipse workspace with a default template that leaves all set up but to compile our extension. It also includes a wizard to easily generate installables. These wizards are accessible through the gvSIG application, at the application menu.

Org.gvsig.tools is the basic infrastructure library to develop plugins.The main functionality is focused on the registration of extension points, utilities to separate API, implementations, SPI (service provider), and monitoring tasks (which in version 1.0 used to freeze the application).This library also supports events, persistence, etc …

A library is a jar. When our application contains the jar, org.gvsig.tools prepares and initializes this library within the core of gvSIG. The classes in the library implement the interface Library (AbstractLibrary).

The managers (PluginsManager) is the entry point of the features. They are like factories (singletons) (at least one per library) that raises the request of the functionality included in the library. It also saves the configuration of the module.

The locators (PluginsLocator) allow to register implementations of managers.We can recover a specific manager API. “Give me the manager of this library.”

A Plugin is a piece that adds a functionality: buttons and toolbars, menu options, data providers and types of documents. Andami has not evolved much since the gvSIG version 1.x. Andami is the framework for the plugins.

The plugin will always have at least two files:

  • config.xml indicating the classes that implement the plug-in units and menus
  • package.info indicating the version, name, build, … of the plugin.

An extension (IExtension) is a set of tools associated with a plugin inside a toolbar or menu and they work together. A group of plugins, you may say. The extension that implements ExclusiveUIExtension specify what tools are or not visible, without touching the core code in gvSIG.

To create a new plugin, we make use of the tool menu generation of plugins available from the development version of gvSIG. This generates the workspace automatically and installs the plugin on the gvSIG from which we generated the plugin. If you have no development release of gvSIG, you will have to compile the sources.

You should be starting a plugin with the wizard while reading this notes or you will be lost.

The plugin consists of two maven projects: org.gvsig.plugin and org.gvsig.plugin.app. org.gvsig.plugin provide the functionality of the library independently of gvSIG (business logic). May have library dependencies on gvSIG, but should be able to operate without having to open the application. That is, it requires nothing of Andami, for example. In org.gvsig.plugin.app.mainplugin (within org.gvsig.plugin.app) we will implement the gvSIG functionality.

The “api” packages should contain interfaces and the “impl” packages should contain implementations.

The workspace is ready to work with Eclipse if we import the project with the maven plugin. If we took an appropriate template to generate the plugin sources, almost all the work is done (except for the exact business logic of our plugin).

It is important to have a java project to test our plugin with its own main, without having to start gvSIG. Also it is recommended that the library has unit tests. That is, we can make an application with the full power of gvSIG, but without using gvSIG itself, ie as if gvSIG were a powerful library GIS. Conclusion: if we do well, we could even use our plugin into another no gvSIG application … as Gofleet.

Each plugin has its own installer, which also is created by wizard inside the gvSIG application.

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